The overall goal of this program is to develop a safe and reliable, non- invasive, transcutaneous pCO2 sensor to track arterial CO2 in neonates at an operating temperature of 37-38 degrees C. Such a device would offer a significant improvement in neonatal care by eliminating the disadvantages of commercially available CO2 sensors for transcutaneous application which have to be heated to 42-44 degrees C, can cause burns in neonates, and as a precaution, have to be frequently moved. In the Phase I program, the Giner, Inc. blood-gas sensor was successfully translated to a 2-dimensional disk configuration using a solid polymer electrolyte proton exchange membrane (PEM) as both the immobilized electrolyte and the supporting structure for the sensing electrodes. More than a dozen of such sensors were fabricated successfully and packaged in a simple enclosure suitable for easy use. The in vitro testing clearly demonstrated that such sensors can exhibit an accurate, linear response to changes in CO2 partial pressure within and beyond the physiologic range. Based on these results, the proposed Phase II study will focus on the improvement of the sensor design to address the issues identified in the Phase I study, followed by proof-of-concept testing with neonates. The two central goals of the Phase II program are to fabricate a gas sensor with a fast, accurate, linear response to CO, partial pressure, and to demonstrate safe and reliable transcutaneous tracking of arterial CO2 levels at 37-38 degrees C in neonates. PROPOSED COMMERCIAL APPLICATION: A reliable, non-invasive pCO2 sensor that operates at 37 degrees C is expected to have substantial commercial application in neonatal care and may prove to be applicable, also, for blood-gas monitoring in post-operative recovery and for patients with chronic obstructive lung disease.